Run-out of a gear is technically the maximum variation of the distance between a surface of revolution and a datum surface, measured perpendicularly to that datum surface. Run-out of a gear relative to a master gear can be measured by bringing the two into meshed engagement, rotating them, and measuring the variation between the center lines of the reference gear and the measured gear during that rotation. Run-out can result in accumulated pitch variation in the rotation of a pair of meshing gears resulting in a non-uniform transfer of motion.
In the past, in shop practice the run-out of a gear has been measured with a dial indicator over pins or balls.
Automatic machines have been proposed for automatically gauging a gear to be measured for run-out with a master gear while both are in close meshed engagement during a full 360 degree rotation. U.S. Pat. No. 4,488,359 to Misson discloses a system in which a gear to be measured is rotatably supported and moved into tight meshed engagement with a master gear and for rotating the gear to be measured and sensing the variation in center-to-center distance between the gears during this rotation.
In many mechanical systems such as transmissions, cluster gears are utilized which constitute two or more gears of different sizes mounted on the same shaft and often formed on the same gear blank, and it is difficult to measure the run-out of each of the gears of the cluster and of the cluster itself using conventional prior art practices and machinery.